Extinctions and EcoArks
The K-T extinction event that heralded the end of the dinos and the rise of mammals is widely believed to have been caused by atmospheric heating from the asteroid that impacted the Gulf of Mexico some 65 million years ago, causing the Chicxulub crater. The theory is that the kinetic energy of the asteroid converted to thermal as it came through the atmosphere, and briefly heated the global air temp hot enough to cook meat. The critters that survived were generally small burrowing animals (e.g., mammals, snakes, and dinosaurs that became modern birds) or aquatic (e.g., fish, crocodilians, turtles) that were protected during the catastrophe.In terms of death toll, however, the K-T pales in comparision to P-T extinction 252 million years ago. The evidence for cause is far less conclusive, but a leading theory is that the atmosphere quickly became anoxic, with poisonous (hydrogen sulfide and/or methane hydrate) gases bubbling out of the oceans. Dinosaurs and mammals both survived due to their efficient lung design. Large insects (such as the giant dragon flies) and many amphibians were too reliant on 30% atmospheric oxygen and died out. Possible triggers for this dramatic atmospheric change may have been some combination of volcanism, continental drift, and asteroid impact causing chemistry and temperature changes to the ocean, and hence induce bacterial blooms to cataclysmically change the atmospheric makeup.
My takeaway lesson from these examples is that you can't trust the Earth's atmosphere over the long term. The allegory of Noah's Ark was probably on the right track - it's always good to be prepared. The other piece Noah got right was the biodiversity of breeding stock. For better or worse, humans require a complex food chain; I suspect any stable closed ecosystem does as well.
My Growing EcoArk
This summer has been a season of acquisition, adding to my aquarium stock and plumbing. An unintended consequence of outsourcing procurement operations to my freecycling, garage saling, craiglisting wife, is that many of the enclosures are already inhabited. I'm not convinced that it is entirely coincidence-- she's long had a love of exotic critters. Hence, we are now incorporating a ribbon snake, a woodhouse toad, a fluctuating number of minnows, 3 silver dollar fish, an indeterminate number of hermit crabs, and 2 dwarf frogs.So far my ark contains representation from the phyla of Chordata (humans, reptiles, amphibians, fish, considering fowl), Annelida (earth worms), and Arthropoda (honey bees, pill bugs, crabs, considering crawdads and black soldier flies). Other phyla for consideration are Rotifera, Tardigrada and Mollusca, I'm not convinced yet of the utility of all the other various (round, flat, jaw, etc) worm phyla and other saltwater primitives (sponges, jellyfish, echinoderms).
The minnows are a PetSmart acquisition to feed the snake. Apparently, goldfish are not nutritious enough. Also, apparently the goldfish is not compatible with the silver dollars. I am inclined to throw the frogs in with the goldfish now that we've got a 5 gal aquarium. I'm now in the process of changing the silver dollars and remaining minnows from a 27G to a 40G tank. The silver dollars require a heater, of which I'm not fond. We're considering changing the minnows over to platys, which can hopefully breed well to keep the snake fed.
Other than population control of the minnows / anticipated platys, I'm not entirely sure what the function of the snake would be in my CELSS. A bit like a self licking ice cream cone... . Not that I have anything against snakes, but if I need a reptilian representative for my ark, my preference would be turtle. Not only do they have fewer bones (ever eat snake?), turtles are nature's Campbell's soup, even providing the bowl. Snakes are finnicky eaters, and only carnivorous- this ribbon snake seems to only eat fish, the insects we've put in his cage all died of old age. Turtles (and tortoise) can be fed from table scraps. The downside perhaps is that they are not exactly prolific breeders.
The hermit crabs are also scavengers, and are the most popular pets we've had yet. My kids love to take them out to the sandbox and make castles for them. We've put the toad in with the crabs, since they both have similar habitat requirements, and both eat pill bugs (which help to breakdown waste, and are easily caught by my kids). The crabs are almost ideal for a CELSS. I say almost, because they are reliant on conch shells for protection and need brine to reproduce. I'm leaning toward crawdads for crustacean representation, since I know they are edible and can cohabitate with freshwater fish.
My Extinctions
My worms disappeared. I suspect bad sawdust from treated lumber as the culprit, although I will cop to throwing in an odd lemon rind as well. While I do have a second composter, it is not populated with worms. Clearly, there needs to be a level of redundancy. Fortunately for me, the garden supply store can provide it this time around.This situation has worried me with the bees as well, particularly since they breed as a colony and are less dependable to source. Subsequently, I've built a second topbar hive, in preparation for next spring's swarm season. Don't worry, they currently are going strong and I plan to harvest some honey this month.